Nice! You might have let it go a little too long though, the white spot in the middle seems to indicate that. Though, it only looks white right on the surface (where it's in contact with the growth chamber) so that's not anything to really be too concerned about. Nice 3D growth!!

Just some additional info, switched skimmer off now since with algae scrubber, both running a bit too efficient as had outbreak of dinos. So far skimmer off and scrubber running, have slightly dirtier tank so keeping dinos at bay